Antimicrobial Activity of Silver Diamine Fluoride and Sodium Fluoride Varnish Against Oral Bacteria: An In Vitro Comparative Study

Background and aim Silver diamine fluoride (SDF) and sodium fluoride varnishes are used in caries management, but few studies have compared their antimicrobial activity head-to-head under standardized conditions. The present study aimed to compare the antimicrobial activity of two commercial silver diamine fluoride (SDF) formulations (Advantage Arrest and Riva Star Aqua), two 5% sodium fluoride varnishes (NovaBrighte and 3M ESPE Vanish), and two SDF-varnish combinations (Riva Star Aqua + 3M ESPE Vanish and Advantage Arrest + NovaBrighte) against Streptococcus mutans, Porphyromonas gingivalis, Staphylococcus aureus, and Lactobacillus acidophilus using an agar disk diffusion assay, with antimicrobial activity quantified by measurement of zones of inhibition. The null hypothesis was that there would be no statistically significant differences in antimicrobial activity among the tested agents or between individual and combination therapies. Methods Standardized agar disk diffusion assays were performed in three independent trials. Seven groups were tested as follows: untreated control, Riva Star Aqua, Advantage Arrest, 3M ESPE Vanish, NovaBrighte, Riva Star Aqua+3M ESPE Vanish, and Advantage Arrest+NovaBrighte. Per-species one-way ANOVA with Tukey post hoc tests and independent-samples t-tests were used to compare inhibition zones among the treatment groups and for pre-specified pairwise comparisons, respectively (α=0.05). Results All per-species ANOVA models were statistically significant (p0.05). Conclusions SDF Advantage Arrest, alone and combined with NovaBrighte, showed the strongest antimicrobial effect. 3M ESPE Vanish had no direct antibacterial activity, while NovaBrighte did, highlighting formulation-dependent differences among sodium fluoride (NaF) varnishes.